The last 1.5 weeks or so I've been working on new documentation.
I've just finished the PDF document and it's available here.
I've been looking into what tiles can be created other than those already mentioned in the 2008 Specifications document.
Nothing extremely interesting, but levels can also contain: chompers with blood on them and level doors that are less/more opened than regular open level doors.
Some other weird stuff can be created, but none of that stuff is usable unless you want to create a level that looks buggy.
I may add some of those new tiles - the bloody chompers and stuck level doors - to apoplexy in the future.

Some time ago I tested which types (modifiers) of stuck spikes can hurt (kill) the kid and which can't.
The result:
(0 is the regular non-stuck spike.)
1-4: Hurts.
5-127: Does not hurt. (Note that 10-127 appears glitched.)
128-254: Hurts only when kid falls into them, but not when running through.
255: Does not hurt. (If someone falls into the spikes, its modifier is changed to 255, making trick 4 possible.)

In the mod Arabian Nightmares, level 1 has a few harmless stuck spikes (mod=8) placed among the many harmful ones (mod=1).
To complete the level, you need to fall onto some of the harmless spikes.
Now, these two types look identical, so you can't know in advance which is which, or that harmless spikes even exist!